Posted
by
CowboyNeal
on Thursday September 20, 2007 @09:49PM
from the goes-to-eleven dept.

Iddo Genuth writes "A U.S. based company introduced an
innovative propulsion system that could significantly shorten round trips from Earth to Mars (from two years to only six months) and enable future spaceships to reach Jupiter after one year of space traveling. The system, which may dramatically affect interplanetary space travel is called the Miniature Magnetic Orion (Mini-Mag Orion for short), and is an optimization of the 1958 Orion interplanetary propulsion concept."

It would work just fine... that is, assuming it works at all. The photon drive has a little problem; namely, it requires about 300 megawatts of power to produce a Newton of thrust... and that's at 100% efficiency.

The Orion concept is much more technically feasable, barring any massive breakthroughs in materials and fusion power.

Look, really, where do people like you get your concepts of space travel from?You were probably trying to be humorous, but, really! Lookee here;

1) Start your trip from Earth Orbit, by firing up them engines and transferring into a nice trajectory to our friendly-neighborhood planet Mars.2) ???3) Profit!... no, I mean, half-way through the journey (or actually, just a little bit before half way, to give some leeway for properly transferring into a Mars orbital path), switch off them engines!4) Swing your cra

1) Start your trip from Earth Orbit, by firing up them engines and transferring into a nice trajectory to our friendly-neighborhood planet Mars.2) ???3) Profit!... no, I mean, half-way through the journey (or actually, just a little bit before half way, to give some leeway for properly transferring into a Mars orbital path), switch off them engines!4) Swing your craft around so that the pointy-end is towards the trajectory's rear and the business end (the engines) are pointing towards the trajectory's forward path.5) Fire up them engines again! Hey presto! You're now flying into nuclear explosions!6) ???

6) Go back to school. Go directly to school. Do not pass Go, do not collect $200.
7) Learn about strange new concepts like Galilean Relativity, Newton's Laws of Motion and Inertial Frames of Reference.
7a) And no, I'm not going to link you to Wikipedia's articles on those. You're going to have to go with step six for that.
8) Now that you understand why step five is no different from step one, you can figure out what step six was supposed to be.
9) For extra credit, write "I will not talk out of my ass about Physics" 6x10^24 times on the chalkboard.

The original studies performed extensive studies on this problem. They solved it with a double shock absorber system; by tuning the absorbers and the frequency at which bombs were ejected, they could achieve a constant acceleration of 1-2 g.

speeding up via riding the wave of successive explosions is great for an unmanned craft. For a manned craft, though, I have a couple questions:1. How will people deal with the psychological effect of the never-ending pounding brought by this type of propulsion?

2. Will scientists avoid this issue by instead strapping people into some kind of suspension and using a fewer number of larger explosions to get up-to-speed per day?

3. What effect would that have on a person physically? We know people can take X

A four, six, and eight cylinder engine will have their pistons out of phase from each other as to provide a continuous and smooth power curve. Now compare that with a single piston engine (lawn mower, weed eater...etc) and take notice of the excessive vibration. Even though the crank shaft has counter weights, it's the interleaving of the detonations (and flywheel) that provides smooth motion.

What's the difference? An internal combustion engine is coupled directly from the explosion all the way to the road, well at least in a manual car. The reason you don't feel each explosion though is that instead of using one big one there are thousands of tiny ones so it seems like a smooth motion.

"Dampen" doesn't mean what you think it means. Or rather, it wouldn't if people would stop adding superfluous letters to seem more intelligent.The word is damp. The infinitive is "to damp" and a device which damps is a damper. There's no need for the extra -en unless you want to have a confusing half-synonym for moisten.

On an orion, the pusher plate is connected to the main spacecraft body by shock absorbers. Quite similar to a gun recoil mechanism, I imagine, except that for manned flight it would sp

According to dictionary.com, the first reference on "dampen"is to moisten. The secondary one is "to dull, deaden, depress,restrain". I thought it was pretty obvious that that is theone I meant, but I can see that there is another meaning.Thank you for the correction.

On Orion, yes, I knew that there would be shock absorbers,spreading the impulse out, but there will still be a hugedifference in timing, magnitude, and direction betweenan infernal combustion engine and an Orion.

If you can't tell the difference between explosions contained in an internal combustion engine to power the drive shaft vs. being moved forward by the actual explosions, then I can't help you.

You're missing the point. The explosions in your car happen very very fast, and the bulk of the vehicle absorbs most of the shock; with the combination of these two effects, you don't perceive them as explosions. Ditto for an Orion drive. As an intermediate case, consider a pulsejet, which is "moved forward by the a

It's now more popular to be a nerd, rather than just a state of being for people who are truly drawn to it, so you start getting a lot of wannabe's who can't hack it intellectually, but are still drawn to the "lifestyle", or more the perks of being known as a nerd. For example, look at Apple users;)

1. lot of explosions in a car engine, and we're all mostly still sane. Seriously though they are small contained explosions (couple grams of material) that vent plasma, there is no reason why people in the passenger compartment would even be aware of each individual explosion. The point is that these are nuclear weapon sized explosions, but many smaller ones providing relatively constant thrust. It won't be jerky.

2. I don't know if you understand how acceleration works. But Fewer larger explosions would make for a rougher ride. And you don't get up to speed on a day to day basis, that would be a weird way to fly a space craft.

3. 1 g constant acceleration for a few hours is pretty freaking fast. This engine could do the thrust of the space shuttle - which is more then 1 g, but why would you do 12 g for more then a few minutes? If you do 1g acceleration for a full day you are going about After 1 day, you are going 800,000 m/s - 800km/sec or 288,000 km/hour mars is about 78million km away - so you can see how this is going, if you stop accelerating at this speed it's about a 4 or 5 million km a day just coasting, or 20 or so days to get there. So it's silly to do more then 1g acceleration, unless you are leaving a planets surface and need to reach escape velocity. So no worries about weird physical effects from the acceleration - now long term zero g is a whole'nother type of problem, but again no need to make it a long trip with this kind of power.

Ah, impulse power. I think early trekkies explained that as more of a Dean Drive (one that dumped half the inertia into a form of parallel-universe oubliette thingy) rather than the fusion "digit ships" of Footfall, which tended to buzz a bit. Some interesting speculative weaponry comes out of Niven/Pournelle books.

The linked article page is not coming up, but I think nuclear is being proposed to use nuclear fuels to superheat gasses for propulsion, so it could be a constant burn and not a series of explosions. At least it's not going to behave like a series of a-bombs, that's stupid.

The full press release notes that the maximum acceleration would be a mere.6 G's or so, which is more than Mars but obviously less than Earth. This is unlikely to result in any unknown physiological changes. In fact, the at least occasional exposure to g-forces would probably be beneficial compared to continuous micro-gravity.

Anyway, a 100 metric ton craft would be pretty wimpy. That's 5% of the Space Shuttle's mass, for instance. I suspect this would be an unmanned mission. (For reference, the Apollo Service Module & Lunar Module together were about 40 metric tons and the longest Apollo missions only lasted 12 days).

Also, the 'ignition mass' for the fastest version would be a whopping 1300 metric tons of plutonium. Using uranium prices as a stand-in, that's about $300 million in fuel. That's an awful big price tag for just getting a larger probe to Mars faster.

I think many of your concerns would be addressed by the addition of an inertial compensator [wikipedia.org]. As the wikipedia article points out, this may not fully protect against sudden shocks. It also seems less effective on people suffering from HPD (hamminess personality disorder), who may be thrown about much more violently than people less drama prone.

(Sorry, reflexive poke at Wyoming. Wyoming has wonderful people, natural resources, and breathable atmosphere. Mars is 0 for 3. Jupiter doesn't even have a surface to land on, but now we can hurry up to get there and not land on it! Like the robot we're sending had some place it would rather be for the marginal time...)

If we weren't killed by the radiation* [abc.net.au] first. The gravity is only 2.2 g; not comfortable, but you could get around; very slowly.

* Jupiter actually gives off more heat than it gets from the Sun. This heat comes from two sources - the slow collapse of the solid core, and the heat of decay from various radioactive trace elements. This energy appears as radiation, and as various radio signals. The radiation from Jupiter at close range is enough to kill an unprotected human within minutes.

First off, I am not a rocket scientist, but I am studying for a BS in Aerospace Engineering.

How exactly is this supposed to reduce travel time? Current lengths of travel are not due to a lack of available thrust or due to amount of fuel available but rather the path taken to reach the destination. Currently in order to travel to say Mars Hohman transfers [wikipedia.org] are often used. These paths and others like them take a certain amount of time to complete, and stronger engines or more available Delta-V allow only for more instantaneous entrances of the transfers or more allowed change in course once at the ship's destination.

In order to reduce time traveled a different orbital mechanic is needed. Even if a ship were to travel in a straight line toward a destination at a rapid enough speed that it would not have to meet up with it too much further along in its orbit it would have to be able to kill relative speed quickly enough to enter a capture orbit.

n order to reduce time traveled a different orbital mechanic is needed. Even if a ship were to travel in a straight line toward a destination at a rapid enough speed that it would not have to meet up with it too much further along in its orbit it would have to be able to kill relative speed quickly enough to enter a capture orbit.

My guess is that it turns around about half way during the trip to start slowing down.

My guess is that it turns around about half way during the trip to start slowing down.

Wouldn't necessarily be half way, we're not talking linear vectors are we? If we're playing catch-up with a planetary target the crossover point might be a bit later than km/2. It's more expensive to escape the closer you are to the sun's gravity well, but I'd think a lot of the energy would be soaked relative to the velocity of the target, i.e. there may not be as much energy to dump near the target. Space ain't flat, found that out from my office mate who was doing the orbital geometry for Pioneer Venus 12/13 some years back (which had the inverse effect, being inward from EO).

I don't know why he kept a separate set of comps in furlongs per fortnight, but us programmerz was wierd back then.

As I recall, Hohman orbits are nice ellipses with body A at perisol and body B and aposol. You make a burn to get into it and out of it; the delta-v required is the difference in velocity between a body in a "circular" orbit at that radius and the velocity of a body in the elliptical orbit. If the planet happens to be at that point, you then just need to make another burn to get into orbit. Timing is important.

Even Hohman orbits are too "spendy" for chemically fueled rockets. Thus the complex back-and-forth gravity-assist paths that NASA probes take on the way to the outer planets, and the use of aerobreaking by Mars probes.

Other, faster transfers are possible. You just enter another sort of elliptical orbit whose path intersects earth's orbit when you leave it, and the destination planet's orbit at a time when the planet will be there. Of course, you have to have a spaceship capable of the much greater change in velocity to enter these orbits.

The linked-too documents suggest that the "mini mag" is not only fuel efficient (read: high Isp), but has a decent amount of thrust. This means it CAN make the drastic changes in velocity necessary.

I believe they are using the "Journalist Transfer Orbit." This is a highly specialized piece of orbital mechanics: basically, you take the average distance to the destination as given by Wikipedia and divide by the spacecraft's top speed.

Current lengths of travel are not due to a lack of available thrust or due to amount of fuel available but rather the path taken to reach the destination.

Of course they are. The available thrust determines the path taken. Basically, the transfer orbit is an elliptical orbit that touches both the inner (in this case Earth's) orbit, and the outer (Mars') orbit. There is a burn at the start, to kick the craft into the transfer orbit, and a burn at the end, to knock the craft out of the transfer orbit. I

Ask your professor about a "chase maneuver." that should get you on the right track.

Hohman Transfers are nice because they are minimum energy transfers (and not necessarily that if you've got more than two bodies and a lot of patience) if you've got a high-thrust impulse engine. (as in, it's only capable of short bursts of high thrusts. compare to continuous thrust options as seen in Deep Space 1.)

They are by no means the minimum time transfer if you've got Delta-V to spare.

First off, I am not a rocket scientist, but I am studying for a BS in Aerospace Engineering.

At what level? A sophmore in high school? (Translated: I love how people wave about unrelated credentials as if it gives weight to what they are talking about.)

How exactly is this supposed to reduce travel time? Current lengths of travel are not due to a lack of available thrust or due to amount of fuel available but rather the path taken to reach the destination.

and enable future spaceships to reach Jupiter after one year of space traveling.

The New Horizons probe, heading to Pluto, took slightly more than a year to reach Jupiter. However, there was no need to stop (park in orbit) and it didn't need to carry bulky life-support stuff. Thus, it could take the fast train.

The basic idea is to create a small fission (not fusion) explosion using magnetic compression. Nuclear weapons use chemical explosives to create an implosion, and during the implosion the fissionable material is compressed hard enough to get a 1.5x to (maybe) 2x density increase.
With magnetic compression, a small pellet can be compressed hard enough to get a 10x density increase. This allows smaller explosions, around 50 gigajoules instead of the 20 terajoules of a fission bomb. They want to use curium or californium as the fuel, rather than plutonium.

They also want to use magnetic containment, rather than an Orion-style "pusher plate" sprayed with oil. Unclear if that can be made to work.

The experimental work (they compressed an aluminum cylinder with a big magnet at Sandia) was done back in 2002. This isn't really under active development.

It's not a totally unreasonable idea, but it would be a huge job to make it work. For one thing, the plan is to assemble a large spacecraft in orbit, not to take off from Earth. It doesn't help with the problem of putting mass in orbit.

They also want to use magnetic containment, rather than an Orion-style "pusher plate" sprayed with oil. Unclear if that can be made to work.

Ought to be a cake-walk once they've got the field in place to make it go "bang".

The pellet is ALREADY confined in a mag field. The re-expanding plasma from the explosion dumps much of its energy into compressing the field between the plasma and the conductor that created it, making the field stronger (and dumping a bunch of the energy back into the conductor as electricity for potential reuse or consumption).

Should be easy to create a selective leak in the desired direction and more fields to guide the plasma as it makes its getaway. (In fact the compressed field toward the vehicle can be used as a spring to return some of that collected energy to the plasma, further increasing the exhaust velocity. And/or the energy from the compressed field could be used to create or strengthen the "nozzle" guiding fields, just-in-time to guide the burst of plasma.)

My understanding is that one of the killers (no pun intended) of the Orion concept was that radioactive ejecta from the drive would inevitably find its way to ground-level, even if it was operating in Lunar orbit. It was mentioned in Dyson's book _Project Orion_ that they had estimated the number of annual excess deaths from cancer caused by launching a single Orion from ground as well as from various orbits.Since this concept will still eject various nasty radioisotopes as well, I wonder if they've done t

I've only glanced over the article so far, but it suggests specific impulses in the 10,000 seconds plus range. That's a critical measure of efficiency in a rocket that dictates the velocity it can obtain. The shuttle's SSMEs get about 455 seconds of specific impulse at a high thrust (millions of Newtons) and ion drives, like the one on the DS1 probe, and the like get specific impulses (Isp) of about 3000 seconds at low thrust. (millinewtons). Apparently the Mini-Mag Orion can produce thrust on par with the SSME. Yikes.

We keep hearing about all these great technologies that will whiz us around the solar system but none of them are going to be of much use. Anything remotely nuclear is probably not going to be allowed to opperate in atmosphere. The military might be allowed to make and man such vehicles but I doubt I'll be booking a trip to the moon on such a thing.So as usual until we get some serious work put into cheap methods to get out of the gravity well nobody is going to have any real dreams fulfilled. Maybe some

The common thread that we keep coming back to is that to really do spaceflight, you must have some form of nuclear power. The laws of physics are profoundly strong on this point. Space is too far and gravity is too strong for chemical rockets to really be successful.

The ideal solution is to find a source of uranium in space, beyond Earth's gravity well, such that, we can mine the uranium in space, and fuel nuclear powered spacecraft from perhaps the moon. I don't see that happening any time soon, as, it is my understanding that its is practically a fluke that a relatively small body like Earth should wind up with such a heavy ore at all. The gods were kind to us during our solar system formation, and it feels unlikely that any asteroid should have a significant uranium deposit.

That leaves us to launching live reactors into space from Earth. Unfortunately, despite safety precautions, the environmental movement makes the development of nuclear powered spacecraft a political impossibility. We can't even build a reactor on land without a mountain of red tape and lawsuits from the greens, even when we know that building such reactors are necessary to combat global warming. Putting a nuclear reactor into something that flies is unthinkable to them, and they would surely think that putting a nuclear reactor into a rocket is downright crazy. Even RTGs, relatively benign, are met with protest. Were it up them, there would be no pictures of Saturn at all from Cassini.

In this one area, the left wing claim to scientific curiosity falls flat on its face. The science is not worth the risk. I think the key to be able to do this, really, is going to be to engage the right wing instead and paint such research as a matter of national security. The right wing, despite its proclaimed conservatism, has a penchant for throwing caution into the wind when it suits it. Heck, they'd blow off global warming just to be able to keep driving trucks. Put a nuclear reactor on a spacecraft to get to Mars in a few weeks, sure, why not? For them, though, the issue is going to be why. Doing it just for the science isn't going to cut it. However, the right does have a penchant for engaging in enormous projects for ideological goals - witness the cold war with Russia, the current war on terror and the invasion of Iraq. None of THOSE projects were cheap or short term, and honestly, only the right wing has the zeal needed to overcome failure after failure as would occur in a really long term space colonization project. Even if you disagree with it, religion is an enormously powerful motivator.

Thus, you'll never get many righties to buy into space for the science, or the future profits, because both don't really do much. But if you could sell them space as a religious duty, then by God, they will say screw the left, throw a hundred billion dollars a year into building nuclear rockets that this country needs, all to create christian colonies on planets and take resources from asteroids. If anything, one could always further argue that with the Russians claiming the North Pole, then, the USA has to claim (something), and it may as well be Mars and the asteroid belt. Asking them to void the UN Treaty on claiming stuff on space would elicit an automatic yes - as the right is already predisposed against the UN.

Surely such a project would be better for the world than the war on terror.

The point is this, and this goes for both left and right. We are entering a time of great consequence for the United States, if not the world, and, it is time for us to stop seeing each other as enemies simply because we have different ideologies. We can make our differences work for us, so long as we express what we want for ourselves as individuals, not as collective party members, and from there identify those strengths we have in each other.

In my case, I selfishly want to see the USA building a fleet of nuclear, manned, rockets, mining asteroids, and colonizing other planets. And, if I have to read the

There's a whole planet spread out in pieces between Mars and Jupiter. Should be a few lumps of sub-critical mass in there you can mine.

I kind of agree, kind of disagree with your assertion about the reasons why people would go into space. Right-wing? I don't think so, necessarily -- unless your definition of right wing means people who are most easily influenced. Your equation is cogent but your coefficients are wrong, I think.

It isn't right-wing so much, I'd say rather that it's the category of people

The best way right now to travel around the solar system is on the interplanetary transport network: slow but low cost transports that are great for moving robotic probes efficiently around the solar system.

I think it's premature to worry about building nuclear powered rockets like that; by the time we will actually be ready to send a human to another planet, we'll have completely different technology. Or, perhaps, we can use suspended animation and use the ITN even for human cargo.

Still, this has very little to do with Orion apart from them both being nuclear pulse propulsion. They only call it a successor to Orion because most people are familiar with Orion.

Orion has already been obsoleted by a similar (but much more effective) design using normal-sized nuclear explosions -- Medusa [wikipedia.org]. Medusa reverses the Orion design, having a parachute in front towing the craft, and detonating the explosives in front of the parachute. It uses structures in tension instead of compression (lighter), it allows the explosions to be further from the craft (less radiation), allows a longer acceleration stroke (smoother acceleration), and captures a larger percentage of the explosive energy.

Reading the (now Slashdotted) article, it sounds like this design came directly out of research done into antimatter catalyzed micro-fission [wikipedia.org]. ACMF is a well-proven technology that uses minuscule amounts of antimatter to kickstart or enhance a fission reaction. Because the technology was fairly straightforward and had good returns for antimatter quantities that are reasonable to produce, NASA was funding research into an engine called ICAN [astronautix.com].

I remember that there was some talk of actually launching a small probe based on the concept, but apparently the plan was scrapped. (Probably to help fund manned space travel.) Whatever antimatter confinement technologies they were working on may have led to the development of this new magnetic confinement fission technology. Or it could just be a coincidence.

Either way, nuclear technology of this sort is fairly well developed and is not a pipe dream. At least not from an engineering standpoint. Getting the risk adverse US Government and NASA to actually build one of the many known-quantity engines we have on hand is a completely different ball of wax. They're still trying to get us reliable LEO access (Thank God for Griffin is all I can say), so I doubt we'll be seeing any advanced engines in practice until the CEV/Orion project enters its third phase.

Even if this craft can reach speeds of 10% the speed of light we would still be limited to interplanetary exploration and exploitation (human nature dictates this). As far as interstellar travel goes it would still take about 45 years to send a spacecraft to the nearest star, not to mention the 4.5 year transmission delay. Still interplanetary travel is a big breakthrough if this article can be believed.

The real breakthrough would be an interstellar spacecraft (the realm of Science Fiction at the moment) and this would really open up our galaxy, however a person would have to live for thousands of years to visit each solar system in our galaxy for just one day even assuming travel between each solar system is almost instantaneous. Think "Star gate technology. Well I did say in the realm of Science Fiction:-)

Even if this craft can reach speeds of 10% the speed of light we would still be limited to interplanetary exploration and exploitation (human nature dictates this).

The solar system is a big enough place for exploitation, and when we're done with the planets and their moons we can look at the Kuiper belt. That should keep us busy for the next couple of centuries, at least, and also allow us to use technologies to actually analyze nearby star systems without having to send probes there just yet.

And once the solar system gets too small for use, we probably have the necessary technologies, experience and infrastructure to send something on an interstellar voyage (probably a generation ship or even a small planetoid outfitted with propulsion systems).

The solar system is a big enough place for exploitation, and when we're done with the planets and their moons we can look at the Kuiper belt. That should keep us busy for the next couple of centuries...

And the President said, "Lewis, Clark, I want you to walk around the block of the White House, its plenty big, and there's probably a lot for you to see. When you're done with that, check out Virginia. Once that is done, I want a complete survey of everything east of the Mississippi. That should keep us busy for a century."

Lewis replied, "What about the vast unexplored reaches of the west?"

To which the President slammed his fist into the desk, "Slow down, Sparky, that would take lots of money that would be better spent on the vast wasteland of New Jersey. And, it would take a long time and nothing good would come of it, I'm sure. And, it would take you forever to get the results back to us. And, you'd smell when you got back. Hell, Clark smells already. Now, you guys do as I told you, none of that 'Vast Vision' stuff."

Knowing they were beat, Lewis and Clark resigned themselves to taking a walk around the block.

"Besides," the President said, "When you finish up, you can both do commercials for Lost Horizon Airlines."

And the President said, "Lewis, Clark, I want you to go explore the moon. The country needs inspiration and I am going to provide it for them"Lewis replied, "But, sir we have no way to get to the moon. Why don't we explore all that land out west that we just purchased. Few if any european has ever seen it. Meanwhile we can learn more about the moon with new telescopes, which will make us more prepared if we ever do go there."

To which the president slammed his fist into the desk, "You have no vision! Besides

A treaty is only as good as the signatories. There is no particular reason why the signatories couldn't write and sign a new treaty that just specified that there were to be no nuclear powered satellites in orbit or nuclear weapons in space.

As that is more or less the intent. A spaceship that was nuclear powered would really only be an issue if it was allowed to orbit the earth long enough to fall out of orbit.

Orion operates by exploding a weapon against a thrust plate, so it really qualifies as a weapon, which is at least one reason Orion was cancelled. I'm not sure how the treaty applies to space-based reactors, but theres definitely a large difference between an RTG and reactor as well.

True, although I think the specific ban was on atmospheric (as opposed to underground) nuclear warhead tests that did in Orion. So even if not a weapon, still technically a warhead.

I think if we really wanted to do this now though, we could get the definitions changed, plus it looks like this isnt using a extra warheads we have lying around, but rather imploding chunks of fissible material using magnets, so it may not technically be a warhead anyway.

And, while I'd object to a ban on hammers in general, I wouldn't object to a ban on people swinging hammers within a foot of my face. Scale this up by a few orders of magnitude, and you've got nuclear arms limitation treaties.

no, nuclear weapons in space are banned by treaty.
we use nuclear power in the form of nuclear batterys in space all the time. mostly because they can stand up to the temprature extremes of space, and will outlast the hardware they are installed in. (Vs a alkaline or some other form of battery, which does not have these properties.)

An RTG doesn't count. If they use plutonium, it's Pu-238 (alpha emitter) with a half life of less than 90 years, not Pu-239 which has a 90,000 year half life (fewer watts per gram) and can support a chain reaction (so it's needed for other things). There are lots of them scattered about the former Soviet Union so if you're doing any hiking there, avoid heat-emanating ceramic objects. [iaea.org]

When not using solar panels (conspicuous and vulnerable) Americans like to power their satellites with RTGs. The Soviets put 35 reactor-powered satellites in orbit and only a few RTG-powered satellites. What was forbidden by the treaty was nuclear weapons, specifically including tests. An interstellar spacecraft powered by nuclear explosions would be a great way to sneakily test your weapons in full view of everyone.

Fry: Hey, as long as you don't make me smell Uranus. (laughs)Leela: I don't get it.Professor: I'm sorry, Fry, but astronomers renamed Uranus in 2620 to end that stupid joke once and for all.Fry: Oh. What's it called now?Professor: Urectum.

You do realize that burning coal has put more Uranium into the air than all the atomic explosions combined right?

I'm more worried about Strontium 90 and radioactive iodine.

Given that Hanford deliberately released a BUNCH of radioactive iodine upwind of an indian reservation at least partly to see what its effects would be on the "marginal population" of indians and rednecks downwind (leading to a considerable increase in birth defect constelations and graves' disease), I suspect others are with me on that.

Yes, it was Footfall. For those who missed it, Footfall is a Larry Niven, Jerry Pournelle collaboration about an alien takeover of Earth, and our eventually overthrowing of them. Humans built an orion based ship to launch a number of weapon carriers at the Fithp ships.